Kevin de León will be the first Latino to lead the California Senate since 1883

As a young activist, Kevin de León helped lead a 1994 rally that flooded downtown Los Angeles streets with protesters opposing a ballot measure to cut off government services to immigrants in the country illegally.

Voters approved Proposition 187 anyway, only to see most of it tossed out by the courts. Twenty years later, as a state senator, De León finished the job by pushing through legislation that wiped the last vestiges of the measure from California law.

Now, as the Los Angeles Democrat prepares to take over Wednesday as leader of the state Senate, De León must prove he can balance his political agenda with the demands of the new post: shepherding colleagues with disparate political views onto common ground.

The job of Senate president pro tem requires the former activist to mesh with the patriarchal tendencies of Gov. Jerry Brown, the understated, iron-ore resolve of Assembly Speaker Toni Atkins (D-San Diego) and a Republican caucus that, although a minority, still has some bite.

De León also has the burden of taking over a legislative body that in the last two years has seen felony charges against three senators, one of whom has been convicted.

De León will be sworn in at Walt Disney Concert Hall in Los Angeles, becoming the first Latino to lead the Senate since 1883, when Reginaldo del Valle held the post.

"I've been thinking a lot as I enter a new phase of my life and a new leadership that provides opportunities to help improve the human condition," De León, 47, said in his fifth-floor Sacramento office overlooking Capitol Park. "So I want to come in and attempt to give every kid a fair shot at the California dream."

Raised in poverty by a single mother from Mexico, De León — single with a daughter in college — has carried his activist agenda through eight years in the Legislature. He has championed affirmative action programs, and salvaged a bill providing driver's licenses to immigrants in the country illegally.

At an event last week sponsored by the Public Policy Institute of California, De León voiced support for expanding state healthcare benefits to such immigrants. But he added a major caveat: finding an acceptable way to pay for it — pragmatism more indicative of a seasoned politician than a young ideologue.

"The question now is how do we fiscally put this together … so it's sustainable, so it's not taxing on the general fund," De León said. "I support it fully, we just have to figure out how to do it responsibly.''

Still, De León vowed to not back down from a political agenda that, for years, has drawn pointed criticism from his detractors and letters telling the Los Angeles-born politician to "Go back to Mexico."

His drive for economic reform is also a reflection of his ethnically diverse, largely working-class district.

It includes Koreatown, Chinatown, Thai Town, Filipinotown, Little Tokyo and Little Armenia. He also represents Boyle Heights, Westlake, Pico-Union and MacArthur Park, which are home to many residents with roots in Mexico or Central America.

In a recent speech to 150 senior citizens at the Hollenbeck Palms senior housing complex, De León cited the experience of an aunt who worked as a housekeeper and now in her 70s finds herself without a pension.

De León said she inspired a bill signed by Brown in 2012 that calls for a state-run retirement plan for low-income workers without a pension.

"I'm her Roth IRA," De León said, adding that he helps his aunt each month pay for food, medicine and rent. "A large number of seniors live in poverty. I think it's unjust and it's unfair."

De León's childhood included two-hour bus rides with his mother each day to wealthy San Diego neighborhoods where she cleaned houses. He was carted to the free clinic or across the border to Tijuana if he needed medical care.

Sen. Jim Beall (D-San Jose) said his colleague once drove him to where he lived as a child in a small basement accessed from an alley in Logan Heights.

"He didn't live in the house. He lived under the house. It was pretty stark poverty," Beall said.

De León escaped the streets in part by joining a boxing program at the Barrio Station youth center with his childhood friend Fabian Nuñez, who would go on to become state Assembly speaker.

"They were decent kids," recalled Rachael Ortiz, who has worked at the center for 44 years and is now its executive director. "They were two real serious young men. Headstrong. They grew up in the middle of escalating gang violence, but they didn't identify with the gangs."

De León graduated from San Diego High School and attended UC Santa Barbara for two years before poor grades cost him his financial aid, forcing him to leave school.

Too embarrassed to go home, De León started teaching civics and English for the One-Stop Immigration and Education Center in Santa Barbara.

"I immediately noticed his leadership skills," said Juan Jose Gutierrez, who headed the center at the time and is now president of Vamos Unidos USA. "He was a hands-on guy who did what needed to get done."

It was his work with the immigration center that led De León to join Nuñez and Gutierrez in organizing the massive 1994 Los Angeles rally against Proposition 187.

A video shows a 27-year-old De León onstage as a sea of 80,000 people, many waving Mexican flags, cheer speakers.

As a mariachi band plays "The Star-Spangled Banner," De León can be seen moving around and talking casually with Nuñez and others. The band then plays the Mexican national anthem and De León stops, faces forward and places a hand over his heart.

Some supporters of Proposition 187, including activist Glenn Spencer, said the video raises questions about where De León's loyalties lie.

"The mistake in retrospect is when you are in your early 20s you don't know" better, De León said. "You're a young activist and you sense this [Prop. 187] rhetoric that wasn't just perceived as anti-immigrant, it was felt in the heart and soul as anti-Latino."

Between his stint at the immigration center and his election to the Assembly, De León earned a degree from Pitzer College and worked for the California Teachers Assn. and the National Education Assn.

De León served as campaign manager for Nunez when he was elected to the Assembly. In 2006, with Nuñez's help, De León unexpectedly defeated Christine Chavez, a granddaughter of iconic labor leader Cesar E. Chavez, for an Assembly seat.

Senate colleagues say De León has matured over the years into a thoughtful leader.

De León has "the talent and the desire to do what it will take to keep all 39 of us prima donnas somehow on the same page so we can move things forward for the state of California," said Sen. Mark Leno (D-San Francisco), referring to the 40-member Senate.

Even as Republicans vehemently disagree with De León on many issues, they say they admire his rise from poverty and trust he will be a fair leader.

"When I think of the American dream, I can't think of anybody who embodies it as much as Sen. De León," said Senate GOP leader Bob Huff of Diamond Bar.

De Leon thought his political career might be over in 2009 when he lost a bitter battle with Assemblyman John A. Pérez, also an L.A. Democrat, for the speaker post. He was stripped of his committee chairmanship and shunted off to one of the worst offices in the Capitol.

De León credits Sen. Darrell Steinberg (D-Sacramento), whom he is succeeding as pro tem, with helping him to get elected to the Senate.

He had to overcome a threat to his reputation when his name appeared 56 times in an FBI affidavit that alleged public corruption by state Sen. Ronald S. Calderon (D-Montebello). In the affidavit, Calderon described De León as a legislative ally.

De León was never charged with any wrongdoing. But Democratic businessman Peter Choi, who is challenging De León in the Nov. 4 election, has made a campaign issue of De León's ties to Calderon.

Colleagues say De León never shies away from a good fight.

As a freshman senator in 2011, De León took on Pérez and a popular priest, John Moretta, who were pushing a bill to disband the city of Vernon.

The priest thought the action would help clean up polluting industry in the city, but De León sided with labor and Vernon businesses and led the charge that killed the bill, arguing that it could have cost jobs in his district.

Last month, De León appeared for the first time with Moretta at a rally at the priest's Resurrection Catholic Church.

De León bristled at any suggestion that he was seeking political penance.

"He stood his ground. I stood my ground. I did what I think was right," De León said. "I made a leadership call."